The present invention relates to dissipating heat generated by integrated circuit modules; more specifically, it relates to an efficient and reduced stress package for integrated circuits.
With the advent of multichip modules (MCMs), containing multiple integrated circuit (IC) chips each having many thousands of circuit elements, it has become possible to pack great numbers of electronic components together within a very small volume. As is well known, ICs generate significant amounts of heat during the course of their normal operation. Since most semiconductor or other solid state devices are sensitive to excessive temperatures, a solution to the problem of the generation of heat by IC chips in close proximity to one another in MCMs is of continuing concern to the industry.
A conventional approach to cooling components in electronic systems in which devices contained in MCMs are placed on printed circuit/wire boards or cards is to direct a stream of cooling air across the modules. Additionally, heat sinks may be attached to the module to enhance the effectiveness of the airflow.
Limitation in the cooling capacity of the simple airflow/heat sink approach to cooling has led to the use of another technique, which is a more advanced approach to cooling of card-mounted MCMs. This technique utilizes heat pipe technology. Heat pipes per se are of course, well known and heat pipes in the form of vapor chambers are becoming common. In the related art, there are also teachings of heat pipes/vapor chambers for dissipating the heat generated by electronic components mounted on cards. However, heat pipe/vapor chamber technology has several limitations when applied to MCMs. One limitation is the thermally induced package and especially chip stress caused by a mismatch in the coefficient of thermal expansion (CTE) between the heat pipe/vapor chamber and both the integrated circuit chips and the MCM module substrate. Another limitation is when very thin wall heat pipes/vapor chamber heat vapor chambers are used, the thin walls can flex making such vapor chambers un-suitable for use with land-grid array (LGA) modules which require pressure be maintained on the LGA connection.
Therefore, there is a need for an efficiently cooled MCM that employs vapor chamber cooling while minimizing CTE mismatch induced package and chip stress and is suitable for a wide range of MCM types.
A first aspect of the present invention is an electronic package having one or more components comprising: a substrate having a first coefficient of thermal expansion; a lid attached to the substrate, the lid including a vapor chamber, the lid having a second coefficient of thermal expansion, the first coefficient of thermal expansion matched to the second coefficient of expansion; a thermal transfer medium in contact with a back surface of each component and an outer surface of a lower wall of the lid; and each component electrically connected to a top surface of the substrate.
A second aspect of the present invention is a method for dissipating heat from an electronic package having one or more components comprising: providing a substrate having a first coefficient of thermal expansion; attaching a lid to the substrate, the lid including a vapor chamber, the lid having a second coefficient of thermal expansion; matching the first coefficient of thermal expansion matched to the second coefficient of expansion; providing a thermal transfer medium in contact with a back surface of each component and an outer surface of a lower wall of the lid; and electrically connecting each component to a top surface of the substrate.
A third aspect of the present invention is an 18. An electronic package having one or more components comprising: a substrate having a first coefficient of thermal expansion; a lid attached to the substrate, the lid including a vapor chamber, the lid having a second coefficient of thermal expansion, the first coefficient of thermal expansion between about 25% to about 700% of the second coefficient of expansion; a thermal transfer medium in contact with a back surface of each component and an outer surface of a lower wall of the lid; and each component electrically connected to a top surface of the substrate.